Along with the rapid increase in the amount of electronic information handled in companies and other organizations, a large number of storage subsystems are introduced and operated in the IT systems of organizations. One of the drawbacks of introducing a large number of storage subsystems in a computer system is that the management costs by the administrator of the computer system are increased. The art of storage virtualization is adopted widely, in which multiple storages are enabled to be accessed virtually as a single storage with the aim to facilitate management of multiple storage subsystems.
As one embodiment for virtualizing storages, a configuration is proposed where multiple physical storage subsystems are provided to a superior system such as a host computer utilizing the storage subsystem as a single virtual storage subsystem. For example, Patent Literature 1 discloses an art related to a computer system in which multiple (such as two) physical storage subsystems are mutually connected via a network, and provided as volumes in a single virtual storage subsystem to the host computer.